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For discussion how dietary fats affect cardiovascular health, see Diet and heart disease.

In biochemistry and nutrition, monounsaturated fats are fatty acids that have a single double bond in the fatty acid chain and all the carbon atoms in the chain are single-bonded. Monounsaturated fatty acids are liquids at room temperature. By contrast, polyunsaturated fatty acids have more than one double bond.

Fatty acids are long-chained molecules having a methyl group at one end and a carboxylic acid group at the other end. Fatty acid fluidity increases with increasing number of double bonds. Therefore, monounsaturated fatty acids have a higher melting temperature than polyunsaturated fatty acids but lower than saturated fatty acids.

Common monounsaturated fatty acids are palmitoleic acid (16:1 n−7), cis-vaccenic acid (18:1 n−7) and oleic acid (18:1 n−9). Palmitoleic acid has 16 carbon atoms with the first double bond occurring 7 carbon atoms away from the methyl group (and 9 carbons from the carboxyl end). It can be lengthened to the 18-carbon cis-vaccenic acid. Oleic acid has 18 carbon atoms with the first double bond occurring 9 carbon atoms away from the methyl group. The illustration below shows a molecule of oleic acid.

Olive oil is a key component of the Mediterranean diet, widely regarded as being protective against cardiovascular disease, while Tea-oil Camellia has been a traditional part of Asian food. Although polyunsaturated fats protect against cardiovascular disease by providing more membrane fluidity than monounsaturated fats, they are more vulnerable to lipid peroxidation (rancidity). On the other hand, monounsaturated fatty acids (like saturated fats) promote insulin resistance, whereas polyunsaturated fatty acids are protective against insulin resistance ^[1][2].

Foods containing monounsaturated fats lower LDL cholesterol, while raising HDL cholesterol. ^[3]

Monounsaturated fats are found in natural foods like nuts and avocados, and are the main component of tea seed oil and olive oil (oleic acid). Canola oil is 57%–60% monounsaturated fat, olive oil is about 75% monounsaturated fat while tea seed oil is commonly over 80% monounsaturated fat. Other sources include grapeseed oil, ground nut oil, peanut oil, flaxseed oil, sesame oil, corn oil, popcorn, whole grain wheat, cereal, oatmeal, safflower oil, sunflower oil, tea-oil Camellia.

1. ^ Lovejoy, JC (2002). "The influence of dietary fat on insulin resistance". Current Diabetes Reports 2 (5): 435–440. PMID 12643169. 
2. ^ Satoshi Fukuchi (2004). "Role of Fatty Acid Composition in the Development of Metabolic Disorders in Sucrose-Induced Obese Rats". Experimental Biology and Medicine 229 (6): 486–493. PMID 15169967. 
3. ^ You Can Control Your Cholesterol: A Guide to Low-Cholesterol Living by Merck & Co. Inc.

• High density lipoprotein
• Saturated fat
• Unsaturated fat
  • Polyunsaturated fat

• Fats (Mayo Clinic)
• Types of Fats (Cardiovascular Consultants) <----------------Some "dated" information.
• The Chemistry of Unsaturated Fats